Imaging hypoxia in gliomas

Hypoxia plays a central role in tumour development, angiogenesis, growth and resistance to treatment. Owing to constant developments in medical imaging technology, significant advances have been made towards in vitro and in vivo imaging of hypoxia in a variety of tumours, including gliomas of the central nervous system. The aim of this article is to review the literature on imaging approaches currently available for measuring hypoxia in human gliomas and provide an insight into recent advances and future directions in this field. After a brief overview of hypoxia and its importance in gliomas, several methods of measuring hypoxia will be presented. These range from invasive monitoring by Eppendorf polarographic O-2 microelectrodes, positron electron tomography (PET) tracers based on 2-nitroimidazole compounds [F-18-labelled fluoromisonidazole (F-18-MISO) or 1-(2-[((18))F]fluoro-1-[hydroxymethyl] ethoxy) methyl-2-nitroimidazole (FRP-170)], Cu-64-ATSM Cu-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) or Tc-99m-and Ga-68-labelled metronidazole (MN) agents to advanced MRI methods, such as blood oxygenation level dependent (BOLD) MRI, oxygen-enhanced MRI, diffusion-weighted MRI (DWI-MRI), dynamic contrast-enhanced MRI (DCE-MRI) and H-1-magnetic resonance spectroscopy.